Alistair Cox, chief executive of white-collar recruiter Hays, told the Evening Standard: “It’s in everybody’s interest to try to fill roles with domestic, locally available talent. But if you cannot find what you need locally you need to look further afield.

“Yet our clients are finding that if they need to look outside the EU for highly skilled workers, it’s too onerous.

"We’ve set some arbitrary hurdles around net migration which means small companies would rather leave a job unfilled than risk falling on the wrong side of a shifting law, and big firms are considering relocating.

“My worry is that we’re not going to capture the full potential of the economic recovery if we can’t fill those highly skilled jobs.”

But Cox warned that kind of surge is at risk, pointing at his recent approach by an international pharmaceuticals company that was looking to open a new R&D laboratory. “It had a shortlist of countries to pick from, and the UK was one of those on the list,” he said.

“They needed about 300 highly skilled scientists, and that number of specialists weren’t available locally. But when they asked officials how many non-EU workers they would be allowed to bring in, the answer was, ‘it’s a number that’s less than what you did last year.’

“They were also told that it was uncertain whether the scientists could stay long-term and it would be reassessed in 12 months.

“So the pharma firm instead chose Singapore, whose government said, ‘bring as many skilled workers as you want,’ as well as fast-tracking their permanent residency and offering tax breaks. So the jobs went. That lab could have been in Britain with 300 highly paid jobs, and maybe 1000 lower-level ones in the surrounding area.”

Cox warned: “If you want to build a world-class industry and country, you’ve got to have world-class talent. If that’s not available locally you should be able to get it wherever it comes from.

"We have to be careful we don’t see a migration of high-skilled jobs abroad because companies need the work doing, so relocate. I’m worried we’re losing our competitiveness and missing opportunities.”